diff --git a/spec/lexer.spec.js b/spec/lexer.spec.js
index de0f81370..e24235594 100644
--- a/spec/lexer.spec.js
+++ b/spec/lexer.spec.js
@@ -1,6 +1,6 @@
-const lexerSpec = require('../src/services/search/lexer.js');
+const lexerSpec = require('../src/services/search/lexer');
 
-describe("Lexer", function() {
+describe("Lexer fulltext", () => {
     it("simple lexing", () => {
         expect(lexerSpec("hello world").fulltextTokens)
             .toEqual(["hello", "world"]);
@@ -26,4 +26,36 @@ describe("Lexer", function() {
         expect(lexerSpec("'unfinished quote").fulltextTokens)
             .toEqual(["unfinished quote"]);
     });
+
+    it("parenthesis and symbols in fulltext section are just normal characters", () => {
+        expect(lexerSpec("what's u=p <b(r*t)h>").fulltextTokens)
+            .toEqual(["what's", "u=p", "<b(r*t)h>"]);
+    });
+
+    it("escaping special characters", () => {
+        expect(lexerSpec("hello \\#\\@\\'").fulltextTokens)
+            .toEqual(["hello", "#@'"]);
+    });
+});
+
+describe("Lexer expression", () => {
+    it("simple attribute existence", () => {
+        expect(lexerSpec("#label @relation").expressionTokens)
+            .toEqual(["#label", "@relation"]);
+    });
+
+    it("simple label operators", () => {
+        expect(lexerSpec("#label*=*text").expressionTokens)
+            .toEqual(["#label", "*=*", "text"]);
+    });
+
+    it("spaces in attribute names and values", () => {
+        expect(lexerSpec(`#'long label'="hello o' world" @'long relation'`).expressionTokens)
+            .toEqual(["#long label", "=", "hello o' world", "@long relation"]);
+    });
+
+    it("complex expressions with and, or and parenthesis", () => {
+        expect(lexerSpec(`# (#label=text OR #second=text) AND @relation`).expressionTokens)
+            .toEqual(["#", "(", "#label", "=", "text", "OR", "#second", "=", "text", ")", "AND", "@relation"]);
+    });
 });
diff --git a/src/services/search/lexer.js b/src/services/search/lexer.js
index 02510079d..301355d30 100644
--- a/src/services/search/lexer.js
+++ b/src/services/search/lexer.js
@@ -5,12 +5,20 @@ function lexer(str) {
     let quotes = false;
     let fulltextEnded = false;
     let currentWord = '';
-    let symbol = false;
 
-    function isSymbol(chr) {
+    function isOperatorSymbol(chr) {
         return ['=', '*', '>', '<', '!'].includes(chr);
     }
 
+    function previusOperatorSymbol() {
+        if (currentWord.length === 0) {
+            return false;
+        }
+        else {
+            return isOperatorSymbol(currentWord[currentWord.length - 1]);
+        }
+    }
+
     function finishWord() {
         if (currentWord === '') {
             return;
@@ -42,7 +50,11 @@ function lexer(str) {
         }
         else if (['"', "'", '`'].includes(chr)) {
             if (!quotes) {
-                if (currentWord.length === 0) {
+                if (currentWord.length === 0 || fulltextEnded) {
+                    if (previusOperatorSymbol()) {
+                        finishWord();
+                    }
+
                     quotes = chr;
                 }
                 else {
@@ -63,19 +75,26 @@ function lexer(str) {
             continue;
         }
         else if (!quotes) {
-            if (chr === '#' || chr === '@') {
+            if (currentWord.length === 0 && (chr === '#' || chr === '@')) {
                 fulltextEnded = true;
+                currentWord = chr;
+
                 continue;
             }
             else if (chr === ' ') {
                 finishWord();
                 continue;
             }
-            else if (fulltextEnded && symbol !== isSymbol(chr)) {
+            else if (fulltextEnded && ['(', ')'].includes(chr)) {
+                finishWord();
+                currentWord += chr;
+                finishWord();
+                continue;
+            }
+            else if (fulltextEnded && previusOperatorSymbol() !== isOperatorSymbol(chr)) {
                 finishWord();
 
                 currentWord += chr;
-                symbol = isSymbol(chr);
                 continue;
             }
         }